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flower grower in the CoachellaValley of southern Californialooks doubtfully at the watereasing its way down his field’s

irrigation furrow. He’s using reclaimeddrainage water, but he suspects it’sinfused with multiple salts and traceelements—rendering it unfit for his just-emerging, tender crop of ornamentalsunflowers.

Use of lesser-quality waters is com-mon practice for many growers in thewater-deprived western United States.But these waters, often recycled after useon other crops, may contain dissolvedsalts and ions that can hinder plantgrowth. Compounding the problem isthat many growers and nurseries alongthe California coast must also contendwith seawater intrusion into neighboringfresh groundwater sources.

Because of the difficulties facingfarmers and growers in accessing high-quality water, researchers with the na-tion’s premier salinity research facility—ARS’s George E. Brown, Jr., SalinityLaboratory in Riverside, California—areworking to find crops that can endure de-graded, often saline, groundwater andwastewater without suffering stuntedgrowth or other salt-induced problems.

A scientist who’s investigated salt-tolerant, or halophytic, crops and plantsextensively is Catherine M. Grieve, plantphysiologist and research leader of thePlant Science Research Unit at the River-side laboratory. For more than 20 years,she’s been evaluating the salt-hardinessof a wide range of grain, orchard, andvegetable crops.

More recently, Grieve turned herattention to floricultural crops—thebright and dazzling fresh flowers thatmake their way into decorative vases,wedding chapels, and well-groomedbackyards. And she’s discovered an

attractive bouquet of options for growers.Many of these floral crops do toleratewater loaded with salts, and some evenappear to be fond of it.

A Pretty PlanResearch into salt-resistant flowers

stemmed from an initiative started 6years ago to bring relevant ARS researchto the country’s fast-growing floriculturaland nursery industries. Second only tocorn and soybeans in terms of U.S. cash

value, these businesses—many small andfamily-owned—are busy greening upAmerican streets and backyards. But,while prolific, the industries face a hostof nagging problems—from damaging,exotic insects to diminishing waterresources.

In California, where cut flowers andfoliage for bouquets make up a $300-million-a-year industry, growers arehaving a hard time accessing their mostprecious resource—water. Demand forhigh-quality water continues to increasethrough competition between urban and

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CHRISTY CARTER (K11382-1)

At the USDA-ARS George E. Brown, Jr., Salinity Laboratory, plant physiologist CatherineGrieve (left) and halophyte biologist Christy Carter measure the height of stock (Matthiolaincana) growing in special sand tanks.

Salt-Worthy Flowers Are Stunning—and Sensible

agricultural users. This means growersmay need to rely more on low-qualitywater resources. This water, sometimesrecycled two or three times, canaccumulate high levels of dissolved saltsand ions.

Growers along the California coasthave another hurdle. Seawater intrusion,in which ocean waters trickle into adja-cent underground freshwater sources, hasbecome a problem in southern Cali-fornia. These saline waters get pulled intolocal aquifers as wells and groundwatersupplies are overdrawn.

The laboratory’s research into floralspecies that can withstand waters highin salts or other ions and produce viable,commercially acceptable flowers shouldhelp growers to conserve resources, cutcosts, and become more efficient.

The environment and public wouldalso win. Reusing greenhouse effluentsfor cut-flower production would reducedischarge of fertilizer, inorganic salts,and pesticides into streams, rivers, tidalpools, and other sensitive areas.

The researchers’ strategy is smart, butnot new. Centuries ago, farmers in theMiddle East dealt with salinity by replac-ing salt-sensitive crops, such as wheat,with more salt-tolerant ones, like barley.But while many studies have focused onvegetables and grains that can toleratesalty waters and soils, little work hasbeen done to investigate salt resistancein flowers and nursery crops.

Not All Waters Are Created EqualOne of the researchers’ first projects

was to create different kinds of water.Specifically, they had to decide on thecompositions of waters used to irrigateflower species of interest.

Producing water with a particularchemical profile was the job of soil sci-entist Donald L. Suarez, director of thesalinity laboratory. He’s an expert at pre-dicting changes in the chemical compo-sition of increasingly saline waters.

Salts play an important role in plantdevelopment. Too much salt may stunt

Chief Rose, Celosia argentea var. cristata. Arelatively salt-tolerant plant, Celosiathrives in the brutal heat of SouthernCalifornia summers.

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growth, or even kill a plant, while somesalt compositions may lead to nutrition-al deficiencies.

This was a critical step in the researchbecause the water available to growersin different regions of the state varies inits makeup. These differences result fromgeology, geography, and other factors.For example, waters found in the state’slower, inland valleys of Imperial andCoachella differ from those availablealong the coast.

“Well water that’s contaminated byseawater intrusion contains more sodi-um and chloride,” says Suarez, “whileconcentrated Colorado River water, ex-isting as reclaimed drainage from othercrops, contains relatively more magne-sium and sulfate.”

For the experiments, the researchersfirst used high-quality water to establishthe plants. Then, the seedlings were irri-gated regularly with laboratory-madesolutions containing gradually increas-ing concentrations of salts—chlorides

Christy Carter (left) and Catherine Grieve weigh saltamounts to be added to irrigation waters for upcomingzinnia experiments.

Technician John Draper prepares a greenhouse sand tank to receive plantings of Zinniaelegans. Others pictured are Clyde Wilson, Pamela Watt, and Xuan Liu.

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and sulfates of calcium,magnesium, sodium, andpotassium. The lab’s sandtanks, filled with washedriver sand, supported theplants and mimicked thesystems used by commer-cial greenhouses.

Florist FavoritesOne of Grieve’s first

floral subjects was statice,a plant with small, paper-like, blue or lavenderflowers. Statice is a stapleflower crop, with 3.7 mil-lion bunches of it sold in1998, at a value of almost$4.5 million. An addedbonus, its flowers are longlasting, retaining bright,funnel-shaped flowersthat often deepen in colorwhen dried. Grieve stud-ied two species of statice:Limonium perezii, cultivarBlue Seas, and L. sinua-

tum, cultivar American Beauty.“In much of the literature, statice is

said to be halophytic, or salt-loving,” shesays. “And its native environments in-clude sand dunes and beaches. So I wassurprised it didn’t do better.”

Both species of statice were able tocomplete their life cycles under highlysaline conditions. But stem length andother qualities important for floricultureproduction were diminished. The re-searchers found Blue Seas to be salt sen-sitive and American Beauty to be onlymoderately salt tolerant.

Grieve notes that this finding should-n’t preclude use of the two cultivars inother horticultural settings. “While thesestatice plants weren’t able to obtain op-timal growth under highly saline condi-tions, both have great value as beddingor landscape plants in problem areas,”she says.

Another flower found in almost allflower shops, and commonly spotted in

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perennial gardens, is stock, or Matthiolaincana. This plant, with its stalks ofsmall, bunchy flowers, is known in theindustry for its spicy-sweet fragrance.

Grieve put two different stock culti-vars, Cheerful White and Frolic Carmine,to the salt test. Like statice, the stockstudies revealed the unexpected. “Wefound stock to be surprisingly salt-tolerant, contrary to what was previouslyknown about it,” she says.

The ability to produce stock with aless-costly, saline water source should begood news for California stock growers,who supplied the country’s florists with24 million stems of the flower last year.

Traditional and ExoticBright and bold, sunflowers are na-

tive to North America and often sold atfarmer’s markets across the country.Grieve studied two different ornamentalsunflower cultivars, Moonbright andSunbeam, and found that excess saltsdidn’t affect the diameter of the flowers.Her test waters were typical of those usedfor irrigation in the Coachella Valley,where sunflowers are grown as a fieldcrop.

“The saline conditions did affect stemlength,” says Grieve. “But the size of thesalt-stressed sunflowers, 4- to 5-inchheads on 28- to 30-inch stems, makesthem completely acceptable for the bou-quet market.”

The genus Celosia, of the amaranthfamily, offers blooms that satisfy theflorist or gardener who’s looking for amore unusual plant. Grieve, along withhalophyte biologist Christy T. Carter,studied Celosia argentea, var. cristata.Its velvety, oversized flowers arecrinkled, suggesting the wavy surface ofbrain coral.

The researchers found the Chief Goldvariety of Celosia to be highly salt toler-ant—and versatile. “It can be producedwith waters contaminated with seawater,like those found along the coast, and withconcentrated river water available in theImperial and Coachella valleys,” says

In a large room located under the sand tanks are 24 reservoirs containing about 2,000 litersof varying-strength saline solutions used to irrigate test plants. Don Suarez, salinitylaboratory director, and Christy Carter measure and record pH and electrical conductivity.

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Grieve. “The other variety we examined,Chief Rose, is better suited for produc-tion with concentrated Colorado Riverwater. It should feel right at home in theinland valleys; it’s compatible with theirwaters and high temperatures.”

From Lab to GrowerFlower growers like Michael Mellano,

senior vice president of Mellano & Com-pany in San Luis Rey, California, areeager to reap the benefits of the River-side lab’s research. “Our company, whichcultivates an array of cut flowers, includ-ing sunflowers and stock, has access toreclaimed waters in Carlsbad, California,north of San Diego. But we’ve been un-sure whether we could use this water be-cause of the salts it contains. The ARSresearch is of great interest to us.”

Looking ahead, Grieve would like tosee how various container crops andshrubs fare under salty conditions. Butfirst, she and Carter are studying whether

certain cut-flower crops can enduresolutions high in nitrogen and otherfertilizer effluents—typical of thosereleased from nursery operations.

“This research could open the door tomore on-site water recycling and de-creased runoff from field and greenhouseoperations,” says Grieve.—By ErinPeabody, ARS.

This research is part of Water Qualityand Management (#201) and PlantBiological and Molecular Processes(#302), two ARS National Programsdescribed on the World Wide Web atwww.nps.ars.usda.gov.

Catherine M. Grieve is at the USDA-ARS George E. Brown, Jr., SalinityLaboratory, 450 W. Big Springs Rd.,Riverside, CA 92507; phone (909) 369-4836, fax (909) 342-4963, e-mail cgrieve@ussl.ars.usda.gov. ★

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